This invention relates to thin film magnetic heads and more particularly to a thin film magnetic head which is improved in magnetic efficiency and yield rate during manufacture.
A thin film magnetic head as shown in FIG. 1 has hitherto been proposed which comprises a non-magnetic substrate 1, a non-magnetic insulating layer 2 formed thereon, and a lower magnetic layer 3, a plurality of non-magnetic insulating layers 4, 5 and 6, a conductive layer 7, an upper magnetic layer 8 and a protective layer 9 which are formed in succession on the layer 2. For details of such a thin film magnetic head, one may refer to U.S. Pat. No. 4,190,872. In the thin film magnetic head constructed as above, due to the thickness of the lower magnetic layer 3 a stepped or raised region is inevitably built, and without removal of the raised region in the subsequent process of the thin-film formation, the upper magnetic layer 8 has a large step or a level-difference at a portion 40 near the gap, thus causing such a problem that magnetic efficiency is degraded. Further, many difficulties are involved in the manufacture process of the thin film magnetic head having such a large level-difference structure, thus resulting in an extremely degraded yield rate.
If an attempt is made to reduce the level-difference by making the lower magnetic layer 3 thinner, magnetic efficiency will be disadvantageously degraded owing to magnetic saturation. On the other hand, the distance between the lower magnetic layer 3 and the upper magnetic layer 8 is required to be large in order to enhance magnetic efficiency, as described in detail in a publication IEEE TRANSACTIONS ON MAGNETICS, Vol. MAG-15, No. 3, July 1979, page 1130. To make this distance large, it is necessary to make the non-magnetic insulating layers 5 and 6 thick, and then a similar large level-difference structure results, imposing a problem on the formation of the conductive layer 7 and the upper magnetic layer 8.
Furthermore, in the structure proposed in prior art the upper magnetic layer 8 comes in contact with the lower magnetic layer 3 at a back gap portion 41, resulting in a large level-difference there. To mitigate the large level-difference, a separate back magnetic layer 42 is formed on the back gap portion 41 simultaneously with the formation of the lower magnetic layer 3. This inevitably increases the number of manufacture processes.